MetroPCS's LG handsets have registered 35% lower drain since last fall, but VoLTE still less far less efficient than 2G voice

Vendors are addressing the problems of battery drain in devices supporting VoLTE (Voice over LTE), but they have a long way to go to match the efficiency of 2G voice. This was the latest conclusion from testing firm Spirent, which highlighted the battery issues associated with VoLTE last year.

Its follow-up testing exercise found major improvements in the efficiency of the carrier VoIP technology, the only network-based way to support voice on LTE-only systems. Only a handful of carriers are implementing VoLTE in the near term, because of challenges including limited device support and 4G coverage. However, there are some frontrunners like MetroPCS, while Verizon is keen to move to LTE-only as quickly as possible, sacrificing circuit switched voice with its history of being optimized for power efficiency.

Last year, tests conducted by Spirent on MetroPCS's service found that 4G calls drained twice as much battery as regular CDMA ones. Four months later, new tests, based on MetroPCS's latest VoLTE handset, the LG Spirit 4G, found that the drain from a 4G call had fallen by 35% compared to the handset's predecessor, the LG Connect.

This is a significant improvement which holds out hope for an acceptable VoLTE user experience once the technology becomes mainstream from 2014. However, it still lags well behind 2G.

The main reason for the dramatic improvement seen in the new LG phone was its use of an integrated CDMA/LTE baseband, rather than separate chips, and the Spirit also has a larger battery. The change also boosted CDMA voice battery life by 18%. The tests indicated that the Spirit would support 875 minutes of talk time in CDMA mode, and 575 minutes when solely making 4G calls.

"We conducted this second round of VoLTE battery performance tests to gain some understanding of whether recent technology advances have helped decrease battery drain and improve capacity for VoLTE calls," said Nigel Wright, VP of wireless at Spirent.